Got hit with this error recently during an upgrade.
$ git xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
The quick fix is to issue the command
xcode-select install then follow the steps prompted to get the latest tools installed.
Another possible solution is to issue a reset like
sudo xcode-select --reset so that xcode will reset and clean up the installed version.
If there is any problem completing these steps you can also just navigate to the Apple Developer site, log in, and issue a search for the developer tools. Searching specifically for “command line tools for xcode” should get the results and bubble the most recent version to the top. Downloading the *.dmg will give you a downloaded installer to get the latest installed. This is of course what the above command pretty much does but just follows a more specific path without as many steps.
These steps *should* get everything back up and running after an upgrade of MacOS or other significant upgrades that need the command line tools upgraded to the latest.